Why use a chrome box with MSD

[AmadeusCharger500]

At Carlisle this year I saw several cars with MSD boxes, they also had either the chrome or orange box on the same car.
Why do some people run with them both.
What are the advantages/disad of just using the MSD box alone?

[dodge freak]

Well I am guessing but maybe they were not hook up. As far as I know you can not run both at the same time. Now I have a MSD 6a box and a MSD 7al box and 2 coils on my car. Only the 7al I am using but the 6a is a back up just in case, all I need to do is swap 2 wires at the battery and switch coil wires and dist plugs. Thats it, the hot turn on wire I leave hook up , I don't have a tach , but it will run. The MSD 7 has never gave out but since I had the 6 on I left it. I also could run the MSD box from the trunk and have a chrome box in front if I wanted too. Sounds like what those guys should be doing.

[doctorpimp]

 
I have MSD 6a.  Mopar Electronic Ign's Chrome box isn't used at all.  I took mine out.  You could keep it there as back-up IF the MSD failed, but I thought it looked messy with all that extra/not used wiring...

[kamkuda]

I know some racers keep a spare in case the other one fails.

[AmadeusCharger500]

I saw a couple cars like this at Carlisle and was curious why the mopar unit was still on there. Didn't have the nerve to ask while I was there.
I also didn't check to see if the wires went nowhere. I guess they must or they are hooked up in some redundant fashion?